Liquid fuel pumps for internal combustion engines



F. M. EVANS July 1, 1958 LIQUID FUEL PUMPS FOR INTERNAL COMBUSTIONENGINES Filed Jan. 16, 1956 2 Sheets-Sheet 1 July 1, 1958 EVANS2,841,085

LIQUID FUEL PUMPS FOR INTERNAL COMBUSTION ENGINES Filed Jan. 16, 1956 2Sheets-Sheet 2 gnm ' Fig.3

United States Patent LIQUID FUEL PUMPS FOR COMBUSTION ENGINES FraserMackie Evans, Acton, London, England, assignor to C. A. V. Limited,London, England Application January 16, 1956, Serial No. 559,484

1 Claim. (Cl. 103-37) 3 This invention has for its object to provide ina simple form a self-governing variable delivery pump for supplyingliquid fuel to a single-cylinder internal combustion engine.

A pump in accordance with the invention comprises a body part havingtherein a pair of intercommunicating bores for reception of feed fueland injection fuel respectively, a plunger in the feed bore, a rotarycam for moving this plunger in one direction and a spring for moving itin the opposite direction, a plunger in the injection bore which ismovable in one direction by the feed plunger and in the oppositedirection by the feed fuel, and a spring-loaded valve for controllingthe rate of flow of fuel from the feed bore to the injection bore.

In the accompanying drawings, Figure 1 is a sectional side elevation ofa pump embodying the invention, and Figure 2 is a fragmentary sectionalview illustrating a modified form of the valve shown in Figure 1. Figure3 is a similar View to Figure 1 illustrating an alternative embodimentof the invention.

Referring to Figure 1 the body part a of the pump has formed in it apair of coaxial bores b, c, of dilferent diameters. The larger bore b isherein referred to as the feed bore, and the other bore c as theinjection bore. At one end of the feed bore is provided a liquid fuelinlet d through which fuel is supplied from a supply tank, and from theother end extends a transfer passage e leading to the inlet of theinjection bore. Between the transfer passage and the inlet end of thefeed bore is provided a restricted vent in the form of bypass passage 1.The latter passage may be of fixed size, or it may be adjustable (asshown) by a manually operable throttle g.

In the feed bore is contained a hollow plunger 11 having at its closedend a port or ports i controlled by a valve j loaded by a spring k andthrough which fuel can pass from the inlet end to the discharge end ofthis bore. For actuating this plunger in one direction there is provideda rotary cam m driven by the engine, the cam being so shaped as toeffect a rapid movement of the plunger in the direction in which thefuel is caused to move through the plunger, and to control the rate atwhich the plunger is returned by an associated spring 12. The action ofthe cam is transmitted to the feed plunger through a cylindrical slide 0contained in a third (and coaxial) bore p in the body or otherassociated part, and an intermediate thrust piece q carried by the bodypart. The range of movement of the thrust piece q in one direction isdetermined by a collar r on one of its ends which can co-operate with ashoulder in the body part, the range of movement in the oppositedirection (under the action of the cam) being determined by an axiallyadjustable stud s on the slide 0.

The injection plunger t is movable in the direction for discharging fuelfrom the injection bore by contact of one of its ends with the feedplunger h, movement in the opposite direction being effected by the feedfuel.

.j. In the discharge outlet u of the injection bore is contained anon-return valve v loaded by a spring w. The

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inflow to this bore may be controlled by either of the followingdevices. In the arrangement illustrated by Figure 1 there is provided anon-return valve x loaded by a spring y and contained in an entrancepassage z situated between this bore and the transfer passage 2 and theflow to the entrance passage is controlled by a piston valve 2 in thetransfer passage. This valve which is loaded by a spring 3 has formed init an axial bore 4 leading to a circumferential groove 5 on the valvethrough which the feed fuel can pass from the transfer passage to theentrance passage. The valve is movable against the action of itsassociated spring by the pressure of the fuel in the transfer passage,so that the rate of fuel supply to the injection bore is progressivelydiminished with increasing feed fuel pressure. Alternatively and asshown by Figure 2, a single spring-loaded piston valve is contained inthe entrance passage, this being adapted to serve both as a non-returnvalve and as a control valve responsive to the pressure'of the feedfuel.

The mode of action of the pump is as follows:

Assuming that both of the bores have already been filled with fuel, theeffect of the action of the cam is to impart to the feed plunger throughthe thrust piece, a movement in the direction which causes fuel to bedisplaced through this plunger from one end of the feed bore to theother. The length of the stroke of the plunger in this direction isdetermined by adjustment of the above mentioned stud s on the sliderelatively to the adjacent end of the' thrust piece. The maximum strokeis obtained when (prior to the commencement of the action of the cam)the thrust piece is in contact with the said stud. Simultaneously withthis movement of the feed plunger, the latter transmits movement to theinjection plunger and so effects discharge of the content of theinjection bore. The manner in which the stroke of the injection plungeris automatically varied will become apparent in a later part of thisdescription.

After the cam has performed its above mentioned duty, the feed plungeris returned by its associated spring at a rate determined by the contourof the cam. During this movement fuel is discharged from the feed borealong the transfer passage to the injection bore and the effect of thisis to move the injection plunger in the same direction as the feedplunger. Assuming that the pump is working at a slow rate the injectionplunger will move at the same rate as the feed plunger, and theinjection bore will receive its maximum amount of fuel. Any excess ofthis amount will be returned to the inlet end of the feed bore throughthe by-pass passage 1.

With increasing rate of rotation of the cam, the pressure of the fuel inthe transfer passage will increase, until a predetermined pressure isreached when the control valve 2 will move against the action of itsspring, in the direction for reducing the rate at which the fuel canenter the injection bore. Consequently the extent of movement of theinjection plunger and the amount of fuel which enters the injection borebefore the cam exerts its next action on the slide Will be diminished,thus providing the desired automatic governing action of the quantity offuel discharged from the injection bore. The speed at which thegoverning action occurs may be varied by appropriate setting of themanually operable throttle g or, in the case of a fixed throttle, byappropriate adjustment of the loading of the spring 3 which opposes themovement of the control valve 2, this adjustment being convenientlyeffected by appropriate manipulation of a screw-threaded bush 3a(Figure 1) which serves as an abutment for the end of the spring remotefrom the control valve.

In the example illustrated by Figure 3, the above mentioned valve j onthe plunger 11 is substituted by a non-return valve 6 loaded by a spring7 and contained in a side passage 8, between the fuel inlet d and oneend of the bore b. In the discharge end of the injection plunger-t isformed an" axial spill bore 9 leading to a circumferential groove 10,and in the body part is formed a spill port 11, so that when the plunger2 approaches the end of its discharge stroke, excess fuel can bediverted from the bore c'to the passage e; The control valve 2 issupported at its lower end on a shoulder 12 in the passage 2 and isprovided with an axial bore 4 which is fed through a side port 13. Thevalve isheld in the position shown by the spring 3, and at the upper endof the bore 4, there is mounted a non-return ball valve 14. Further thethrust piece q is permanently in contact with the parts It and s and theeffective length of stroke of the plunger t is determined by the spillgroove 10 and port 11.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent is:

A liquid fuel pump comprising in combination a fuel inlet, a body partprovided with a first bore for receiving fuel from said fuel inlet, asecond bore arranged co- 4 axially with and extending from one end of.said first bore, and a fuel transfer passage leading from said firstbore to the remote end of said second bore and having a restricted ventassociated"'ther"ewitli, afuel outlet leading from the last mentionedend of said second bore, a fuel feed plunger slidable in said firstbore, a spring acting on said plunger, a rotary cam for moving saidplunger against the action of said spring, a fuel injection plungerslidable in said second bore in one direction by said fuel feed plungerfor discharging fuel through said outlet, and in the oppositedirection'by the pressure of fuel transferred by said fuel feed plungerfrom said first bore to said second bore through said passageway, and aspring-loaded valve arranged in said passageway and movable by fuelpressure in said first bore to reduce the rate of fuel flow therefrom tosaid second bore.

ReferencesCited in the file of this patent UNITED STATES PATENTS2,582,535 Drouot Ian. 15, 1952

